1. Field of the Invention
This invention relates to methods for hydrostatic testing a section of a pipeline that employs a pig train including plugging tools, at least one sealing pig, slugs of fluid between the sealing pig and plugging tools and a pumping system for increasing the hydrostatic pressure interior of the pipeline between spaced apart plugging tools.
2. Description of the Prior Art
The invention herein discloses methods and systems for hydrostatic testing a pipeline.
In North America, Europe and other industrialized areas of the world, vast quantities of fluids, including liquids and gases, are transported through pipelines. These fluids include crude oil, lubricating oil, natural gas, gasoline and so forth. These pipelines are often of considerable length and extend over all types of geographic terrains. Many pipelines today are located underneath rivers and lakes and growing mileages of pipelines are located on the surface of the earth covered by seawater, that is, submerged or subsea pipelines.
In the event of damage, deterioration from age, or changing conditions including need for modification or structural changes to a pipeline, a serious problem rises as to the manner in which the flow of liquid, either fluid or gases, through the pipeline can be controlled during repair, maintenance and testing. Most pipelines in use today are continuously filled with liquids or gases. Since the volume contained in a relatively long length of pipeline is great, the value of the contained fluid is great. In addition, in most instances if it is necessary to repair, replace or test a pipeline it is not feasible to drain the pipeline due not only to the cost of the contents but many of the products carried by pipelines are deleterious to the environment. Many governmental restrictions around the world prohibit discharging pipeline contents into the environment for the purpose of facilitating repair, maintenance or testing.
One method used to test or repair a pipeline is to isolate and evacuate a section of the pipeline by using internally transportable plugging devices or pigs. In order to employ a plugging pig it is necessary to be able to stop the pig at a pre-selected location and by internal means, closing the plugging pig to seal the interior of the pipeline against further fluid flow. When repair, maintenance, testing or so forth is completed, it is then necessary to release the grip of the plugging pig to permit it to resume passage through the interior of the pipeline by the force of fluid flow. In this way, the plugging device in the form of a fluid transportable pig, can be removed from the pipeline after its use has been completed and the pig reused for further applications.
A commonly used method to stop flow in a pipeline temporarily is by the utilization of a product commercially available under the trademark STOPPLE® as manufactured and supplied by T.D. Williamson, Inc. of Tulsa, Oklahoma. A method of use of the STOPPLE® plugging system includes installing an access fitting followed by boring a large diameter hole at each of two extremities of the pipeline to be worked on or tested, inserting a plug in each large hole and pivoting the plug about a transverse axis to plug the pipe. After the repair work is done, the plugs are pivoted back and removed from the hole and large flanges are secured on the fittings. While this system functions successfully in areas where the pipe is readily accessible from the earth's surface, in many locations accessibility is a continuous problem and this is particularly a burdensome problem with pipelines running under lakes, rivers and especially pipelines running on the ocean floor. For this reason and in recent years plugging tools or plugging pigs have been developed. These devices are insertable in the pipeline for movement by fluid flow and can be actuated at a selected point to grip the interior wall while simultaneously sealing the interior wall of the pipeline against fluid flow. The invention herein includes methods, systems and devices for employing such plugging pigs in pipelines particularly for hydrostatic testing of pipelines.
For additional information relating to the background of the subject matter of this invention, reference may be had to the following United States patents and publications:
PatentNumberInventorTitleRE33,160GuthrieMethod and Apparatus For Inspecting Lateralet al.Lines3,746,026HerringPipeline Plugging Pig3,750,711ConklinMethod and Apparatus For Testing For Leakset al.In Pipes3,837,214GuestSelf-Propelled Pipeline Plug3,908,682ThompsonMethods and Apparatuses For Remotely andReleasably Sealing A Pipe Line4,026,329ThompsonMethod and Apparatus For Remotely andReleasably Sealing A Pipeline4,314,577BristerInstallation, Hydrostatic Testing, Repair andModification of Large Diameter Fluid Trans-mission Lines4,441,328BristerMethod and Apparatus For Forming ATemporary Plug In A Submarine Conduit4,484,602GuthriePacker For Sealing Lateral Lines4,691,728MathisonElectronic Test and Seal Apparatus andMethod4,854,384CampbellPipeline Packer4,991,651CampbellPipeline Packer For Plugging A Pipeline AtA Desired Location5,139,576DavisMethod and A Horizontal Pipeline PigLaunching Mechanism For SequentiallyLaunching Pipeline Pigs5,272,646FarmerMethod For Locating Leaks In A FluidPipeline and Apparatus Therefore5,372,162FreyRepair Device For The In Situ Repair ofPipes, And A Method of Repairing Pipes5,433,236ZollingerApparatus For Moving A Pipe Inspectionet al.Probe Through Piping5,842,816CunninghamPig Delivery and Transport System ForSubsea Wells5,983,948Yagi et al.Method of Repairing An Existing PipelineIncluding A Main Pipe and A Branch Pipe6,022,421Bath et al.Method For Remotely Launching Subsea PigsIn Response To Wellhead Pressure Change6,348,869AshworthPipe Leak Detection